"We found that for every minute of tarmac time being
    saved there is, on average, a three-minute increase in
    the total passenger delay," said Vikrant Vaze, an
    assistant professor at Dartmouth's Thayer School of
    Engineering who co-authored the study.

    Adopted in 2010, the Transportation Department rule
    requires that passengers be allowed to deplane within
    three hours of boarding or landing for domestic
    flights. Airlines are subject to fines of up to $27,500
    per passenger for violations.

    Hoping to avoid fines, airlines have been quicker to
    pull the plug on flights, Vaze said. That forces
    passengers to scramble to find another flight to reach
    their destination, something that has become
    increasingly difficult as industry consolidation
    reduces the number of available seats on planes.
    Flights that are not canceled have to start lining up
    anew after letting passengers deplane and then reboard,
    adding to the ultimate delay.

    "Most of these extra delays are being felt by those
    exact same passengers," Vaze said. "It's just that
    they're not on the tarmac."